My 5yo daughter is a similar reading level. She loves the Billie B Brown Mysteries, the Real Pigeons series, the Treehouse series and the Far Out! (June Factor, old school nonsense rhyme books) series.

We had this ongoing problem with DD - at 7 she tested at a 17 y.o level. The school didn't know what to do - they kept sending her home with books on things like the Boxing Day Tsunami, Sadako and the Paper Cranes, Anne Frank - she was utterly traumatised.

We ended up asking the school to stop assigning books to her. Instead we gave her:

Like PP -all the Roald Dahl books
Enid Blyton Books - especially loved the "Naughtiest Girl" series
Billie B
Treehouse series - still insists on the latest one now at 11.
Wonder
Truly Tan series
Ella Diaries

By about 10 we moved onto a lot of non-fiction books and she loves them - (although still asked for Weirdo 13 the other day):
I am Mala
Lion
Happiest Refugee
Hope in a Ballet Shoe (although there is violence which still upsets her)
The Barefoot Surgeon
Walking Free
Helen Keller biography
Wish you Happy Forever

Good luck - I still find it really hard now to find books at her level with minimal sex or violence, but will keep her interested. I have an added problem that she is super lazy. She would sit and read the Hot Dog series all day if I let her!

Thank everyone, I am literally taking notes and will check these suggestions out. It's harder now she is reading independently when she was younger I would read to her and just skip over any awkward/upsetting bits. Now of course that's not an option

Blyton’s The Naughtiest Girl books really are great. Also her St Clare’s school stories might suit- they’re set in a high school boarding school but very tame on the drama front, lots of midnight feats and rambles and playing tricks on the French teacher!